Process for retarding the formation of popcorn polymer formation in olefin monomer recovery system



United States Patent PROCESS FOR RETARDING THE FORMATION OF POPCORN POLYMER FORMATION IN OLEFIN MONOMER RECOVERY SYSTEM Harry Elmer Albert and Paul Gordon Haines, Lafayette Hill, Pa., assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed Jan. 25, 1966, Ser. No. 522,850

4 Claims. (Cl. 260-6665) This invention relates to new compounds which are 1 to 1 molar adducts of a poly-hydroxyphenol and a dialkylhydroxylamine. More specifically, the invention is concerned with compounds having the following formula where R is H, OH or a lower alkyl group having 1 to carbon atoms; R is H, a hydrocarbon group containing 1 to 9 carbon atoms such as methyl, ethyl, t-butyl, amyl, phenyl, benzyl, t-octyl or nonyl, or a carbalkoxy group, C(O)OR where R is an alkyl group containing 1 to 5 carbon atoms; R and R may be the same or different alkyl or substituted alkyl groups containing 1 to 7 carbon atoms such as methyl, ethyl, n-butyl, hydroxyethyl, nhexyl or benzyl, or R and R together with the nitrogen atom may form a 5 or 6 membered ring such as in N- hydroxymorpholine, N-hydroxypiperidine, and the like.

The compounds of the invention are liquids, gels or solids, and have utility as monomer stabilizers, as stopping agents for polymerization systems involving ethylenic ole fins, and as popcorn polymer inhibitors. The compounds are made easily by gentle warming of the reactants (i.e., the polyhydroxyphenol and the substituted hydroxylamine) to give a homogeneous liquid which generally crystallizes on standing. In carrying out the procedure, generally equimolar amounts of the reactants will be used, but it is found that even when 2 moles of the hydroxylamine compound is used per mole of the polyhydroxyphenol the product obtained is the 1 to 1 adduct. In order to further illustrate the invention, the following examples are given:

Example 1.Diethylhydroxylamine-4-t-butylcatechol adduct Forty-nine and nine-tenths grams (0.30 mole) of 4-te rt butylcatechol (M.P. 3842 C.) was dissolved in 31.1 g. (0.30 mole) of 86% diethylhydroxylamine by heating to 70 C. during stirring. A viscous, brown liquid resulted which crystallized on standing at room temperature. After pressing on a porous plate, the melting point was found to be 73-75 C. The mixed melting point with purified 4-tert-butylcatechol (M.P. 5759 C.) was 47-65 C. Analysis gave 5.19% nitrogen; theory for a 1:1 adduct is 5.48% nitrogen. Infrared absorption indicated an adduct structure.

The same product was isolated from a reaction mixture consisting of 2 moles of diethylhydroxylamine per mole of 4-tert-butylcatechol. The product was recrystallized to a constant melting point using hexane as the solvent.

Example 2.Diethylhydroxylamine-catechol adduct A mixture of 8.9 g. (0.1 mole) of 99.7% diethylhydroxylamine and 11.0 g. (0.1 mole) of catechol (M.P. 104-106 C.) was gently warmed until all the catechol had dissolved. The product Was a light yellow liquid at room temperature. Analysis showed it to contain 44.62%

3,417,154 Patented Dec. 17, 1968 diethylhydroxylamine and 7.04% nitrogen. Infrared absorption indicated an adduct structure.

Example 3.Diethylhydroxylamine-3, S-di-t-butyl catechol adduct .resulted. This melted at 46-49 C. Analysis gave 28.4%

diethylhydroxylamine; theory for a 1:1 adduct is 28.6% diethylhydroxylamine. Infrared absorption indicated an adduct structure.

Example 4.Diethylhydroxylamine-pyrogallol adduct A mixture of 3.8 g. (0.03 mole) of pyrogallol (M.P. 133-135 C.) and 5.3 g. (0.06 mole) of 99.7% diethylhydroxylamine was warmed in a beaker on a hot plate until all solids had dissolved. The resulting liquid was placed in a vacuum desiccator over anhydrous calcium chloride. After 1 day, a solid melting at 68-73 C. was obtained. This was pulverized under 200 ml. of n-hexane and filtered to give 5.6 g. of white crystals melting at 72- 7 5 C. Analysis gave 39.6% diethylhydroxylamine; theory for a 1:1 adduct is 41.4% diethylhydroxylamine. The infrared spectrum showed no unchanged starting materials to be present. The same 1:1 adduct was obtained when a 3 :1 mole ratio of diethylhydroxylamine to pyrogallol was used.

Example 5.Diethylhydroxylamine-propyl gallate adduct A mixture of 20.2 g. (0.1 mole) of propyl gallate (M.P. 146-148 C.) and 8.9 g. (0.1 mole) of 99.7% diethylhydroxylamine was warmed in a beaker on a hot plate to give a homogeneous solution. On cooling, a viscous brown tacky gel was obtained. Infrared absorption showed that there were no starting materials present as such in the reaction product.

Additional examples of compounds which illustrate the invention are as follows:

Dimethylhydroxylamine-4-t-butylcatechol N-hydroxymorpholine-4-t-butylcatechol Diethylhydroxylamine-4-benzylcatechol Diethylhydroxylamine-4-phenylcatechol N-hydroxymorpholine-catechol Di-n-butylhydroxylamine-4-t-butylcatechol N-hydroxymorpholine-pyrogallol Diethylhydroxylamine-4-t-amylcatechol N-hydroxymorpholine-4-t-amylcatechol Diethylhydroxylamine-4-methylcatechol Di-n-butylhydroxylamine-pyrogallol Diethylhydroxylamine-S-t-butylpyrogallol Diethylhydroxylamine-3,S-dimethylcatechol N-hydroxymorpholinc-propyl gallate Dimethylhydroxylamine-propyl gallate N-hydroxypiperidinc-propyl gallate As indicated above, the compounds of this invention have been shown to be active as monomer stabilizers, as stopping agents for SBR polymerization, and as popcorn polymer inhibitors.

Evaluation as stabilizers for styrene monomer was carried out using a dilatometer in a manner similar to that described in US. Patent 2,965,685. The dilatometer had a bulb of approximately 25 ml. capacity and an cm. capillary stem of 2 mm. bore. The dilatometer containing the styrene charge was placed in a constant temperature bath maintained at C. As polymerization progressed, the liquid contracted and the level in the capillary progressively fell. Thus a decrease in the liquid 3 4 volume in the capillary was a direct measure of the These results show that the adduct of diethylhydroxylamount of polymerization. The styrene was first distilled amine and 4-t-butylcatechol, the adduct of diethylhyto remove the commercial inhibitor and then the test droxylamine and catechol and the adduct of diethylhycompound was added. A two hour test period at 120 C. droxylamine and propyl gallate are very effective stopping was employed to give the following results: 5 agents for SBR polymerization.

Loss in Height (2 hrs. at 120 0.) Compound (0.5% on styrene) Thus the diethylhydroxylamine-t-butylcatechol adduct Evaluation for popcorn polymer inhibition was carried 1s a very effective styrene stabilizer and is considerably out by tests described in US. 3,148,225 by charging a more effective than 4-tert-butylcatechol, which is used 7 ounce beverage bottle with 30 ml. of inhibitor-free commercially for styrene stabilization. styrene, 1 ml. of butadiene, 0.5 g. of popcorn polymer Using the same dilatometer under different test condiseed and the test inhibitor. The bottles thus prepared,

tions, the effectiveness of a stabilizer for acrylonitrile was including a blank, were then heated in an air oven at measured. Freshly distilled acrylonitrile was employed 140 F. while being checked frequently for growth of and 0.25% of p-methane hydroperoxide was added impopcorn polymer. Using this procedure, the following mediately before use so that appreciable polymerization results were obtained:

would occur in a convenient length of time (2 hours) at a 60 C. The test temperature was limited by the boiling Compound: Result (at 140 No inhibitor Popped after 12 hours. 0.05% diethylhydroxylamine-t-butylcatechol point of acrylonitrile (7879 C.), since having the test temperature too close to the boiling point caused bubble formation in the dilatometer. The following test results were obtained: adduct Popped after 50 days. Inhibitor Loss in height hese results show that the diethylhydroxylamine-t- (0.5% on acrylonitrile) 2 at 0 Q) butylcatechol adduct is an extremely effective inhibitor of Bla k 9 0 popcorn polymer formation. Diethylhydroxylamine-t-but l t h l In a second test series, the following results were dd t 0 obtained:

Compound: Result (at 140 F.) Thus the adduct of diethylhydroxylamine and 4-t-butyl- No inhibitor pp after 12 hours.

catechol completely inhibited the polymerization of acrylonitrile under these test conditions. 005% dlethylhydroxyl' For stopping agent evaluations, a sulfoxylate (SFS) SBR test recipe was employed. For a 7 ounce beverage 40 bottle the following ingredients were used:

aminecatechol adduct Popcorn growth started after 15 daysvery little further growth after 31 days. Grams 0.05% diethylhydroxyl- Butadiene 18 1 Styrene 7 p py s late P d f 14 d Water 5O a duct oppe a ter ays. gggg i g g ggg313 These results show that the adducts of the invention 1 P are ver effective inhibitors 0 0 corn 1 ol mer forma- Dispersant (Daxad 11 0.038 mm. y f p P p y Iron sequesterant (verslmc 100) (L008 It will be understood that the adducts of the invention p'Menthane hydroperoxlde 68? may be used generally to prevent popcor polymers in FCSO4'7H2O 6 the preparation of polymers and copolymers such as those Na3PO4'12H2O 9' obtained from ethylenically unsaturated monomers. For Sodlum Sulfoxylate formaldehyde 0'0169 homopolymers, the unsaturated monomer will be a con- The loaded bottles were agitated by rotating end-overi g t i l The useful conjugated diolefinq e end around the shaft of a polymerizer having a bath empllfied y butfldiefles Such as -Ll 18013111116, held at 5 C. Polymerization was allowed to continue Y P-L chlol'oprenei 219119111147311tadiene, until a conversion of 55 to was obtained, the condlmethylbmadlelleand the llke- 1:118 copolymfifilflblfi version being followed by solids determinations. Then monomer used In P Y formatlol'l and Whlch Will the test stopping agent was injected through the self- 60 normally comprise up to about of the mixture will sealing bottle cap using a hypodermic syringe. Converbe a mono-olefin containing a single CH =CH group sion was again measured after 1 hour at 5 C. and then having at least one of the free valence bonds attached to after 18 hours and 24 hours at 50 C. The following an electronegative group. Such olefins include aromatic results were obtained: olefins such as styrene, vinylnaphthalene, a-methylstyrene,

Percent Conversion Stopping Agent Cone.

(p.h.m.) When After-1hr. After 18 hrs. After 24 hrs.

stopped at 5 C. at 50 C. at 60 C.

Series 1:

None 56. 6 92. 7 02. 8 s Disthylhydroxylamine-t-butylcatech01 adduct 0.15 50.6 55.3 54.5 55.2 530.19 5s. 6 93. 7 no. a

Diethylhydroxylamine-eatechol adduct 0. 15 55. 6 56. 1 55. 0 54. 8

Diethylhydroxylamine-propyl gallate adduct 0. 15 55.6 55. 5 55. 3 55.0

p-chlorostyrene, etc.; the carboxy containing monomers and the corresponding esters, nitriles, and amides such as acrylic acid, methacrylic acid, methylmethacrylate, acrylonitrile, methacrylarnide, and the like, Preferably, this invention will be used in recovering the monomers used to make any butadiene-based polymer latex.

The concentration at which the inhibitor is used will usually range from 0.001 to about 5.0 percent by weight of the total monomers (i.e. about to 50,000 parts per million parts of monomer). At concentrations below this value the inhibiting effects are too small to be'of significant va-lue. On the other hand, greater amounts may be used, say up to but such large amounts are not required and are simply wasteful of inhibitor.

It will be understood that numerous changes and variations may be made from the above description and examples without departing from the spirit and scope of the invention.

We claim:

1. A process for retarding the formation of popcorn polymers in olefin monomer recovery systems, which comprises contacting said monomer with an inhibiting amount of a compound having the structure where R is selected from the group consisting of hydrogen, hydroxyl, and lower alkyl having from one to five carbon atoms, R is selected from the group consisting of hydrogen, a hydrocarbon group containing one to nine carbon atoms, and -COOR where R is an alkyl group containing from one to five carbon atoms, R and R are the same or different alkyl or substituted alkyl groups containing from one to seven carbon atoms and which may together with the nitrogen atom form a five or six-membered ring.

2. The process of claim 1 where the inhibiting agent is an adduct of diethylhydroxylamine and catechol.

3. The process of claim 1 where the inhibiting agent is an adduct of diethylhydroxylamine and 4-t-butylcatechol.

4. The process of claim 1 where the inhibiting agent is an adduct of diethylhydroxylamine and propyl gallate.

References Cited UNITED STATES PATENTS 2,181,102 11/1939 Stoesser et al 26Q-666.5 2,561,916 7/1951 Erickson 260666.5 3,148,225 9/ 1964 Albert 260-6665 JAMES A. SEIDLECK, Primary Examiner.

U.S. Cl. X.R. 

1. A PROCESS FRO RETARDING THE FORMATION OF POPCORN POLYMERS IN OLEFIN MONOMER RECOVERY SYSTEMS, WHICH COMPRISES CONTACTING SAID MONOMER WITH AN INHIBITING AMOUNT OF A COMPOUND HAVING THE STRUCTURE 